A rare-earth-free ultra-wideband near-infrared fluorescent powder and a preparation method and application thereof
By introducing gallium oxide and doping Li⁺ ions into magnesium aluminate, and combining high-energy ball milling and stepwise sintering processes, a rare-earth-free ultrawideband near-infrared phosphor was prepared, solving the problems of rare-earth resource dependence and insufficient performance in the existing technology, and achieving efficient and stable near-infrared luminescence effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XIAMEN UNIV OF TECH
- Filing Date
- 2026-05-08
- Publication Date
- 2026-07-21
AI Technical Summary
Existing near-infrared phosphors rely on rare earth elements, which are scarce and expensive. They also have narrow emission bandwidth and poor thermal stability. Traditional preparation processes make it difficult to control the coordination environment of trivalent chromium ions, thus limiting their broadband emission performance.
Gallium oxide was introduced into magnesium aluminate to adjust the crystal field strength. Li⁺ ions were doped and pretreated with high-energy ball milling, stepwise sintering and acid etching were used to optimize the powder dispersion and crystallinity, thus preparing rare earth-free ultrawideband near-infrared phosphors.
It achieves high stability and high efficiency luminescence performance of rare earth-free ultrawideband near-infrared phosphor, with emission spectrum covering 700-1100nm, internal quantum efficiency ≥96%, luminescence intensity maintained at over 88% at 180℃, and cost reduced by 40%.
Abstract
Description
Technical Field
[0001] This invention relates to the field of solid-state luminescent materials technology, specifically to a rare-earth-free ultrawideband near-infrared phosphor, its preparation method, and its applications. Background Technology
[0002] Near-infrared light sources are urgently needed in fields such as biomedicine and environmental monitoring. However, existing near-infrared phosphors mostly rely on rare earth elements such as Nd³⁺ and Yb³⁺, resulting in resource scarcity and high costs. While existing trivalent chromium ion-doped phosphors have achieved rare earth-free emission, they suffer from drawbacks such as narrow emission bandwidth, poor thermal stability, and insufficient internal quantum efficiency (e.g., the quantum efficiency of existing trivalent chromium ion-doped magnesium aluminate phosphor is only 95%, and the luminescence intensity drops to 70% at 150℃). Furthermore, traditional preparation processes struggle to precisely control the coordination environment of trivalent chromium ions, leading to a low proportion of weak-field centers and limiting broadband emission performance. Therefore, developing a rare earth-free, ultra-wideband, and highly stable near-infrared phosphor is of significant practical importance. Summary of the Invention
[0003] To address the technical shortcomings of existing near-infrared phosphors, such as reliance on rare earth elements, narrow emission bandwidth, and poor thermal stability, this invention provides a rare earth-free ultrawideband near-infrared phosphor, its preparation method, and its applications.
[0004] This invention is achieved through the following technical solution:
[0005] (1) Matrix modification: Gallium oxide is introduced into magnesium aluminate to adjust the crystal field strength and increase the number of weak field trivalent chromium ion centers to achieve ultra-wideband emission;
[0006] (2) Synergistic doping: Li⁺ ion doping reduces lattice distortion, and silicon dioxide breaks the inversion symmetry to improve absorption efficiency. The two work together to enhance luminescence performance.
[0007] (3) Process optimization: High-energy ball milling pretreatment + step-by-step sintering + acid etching process is adopted to improve powder dispersibility and crystallinity and reduce impurities and defects.
[0008] The specific technical solution is as follows:
[0009] A rare-earth-free ultrawideband near-infrared phosphor, with the following general chemical formula: Where 0.005≤a≤0.03, 0.2≤b≤0.8, 0.01≤c≤0.05, and 0.02≤d≤0.08; the phosphor, when excited by blue light at 450-470nm, emits a spectrum covering the near-infrared band of 700-1100nm, with a half-width at half-maximum of ≥200nm, an internal quantum efficiency of ≥96%, and maintains more than 88% of the luminescence intensity at 180℃ compared to room temperature.
[0010] The phosphor has a spinel-type crystal structure with a lattice constant a = 8.08-8.12 Å. Trivalent chromium ions exist as weak field centers, and the self-trapped exciton luminescence contribution rate is ≥85%.
[0011] The method for preparing a rare-earth-free ultrawideband near-infrared phosphor includes the following steps:
[0012] (1) Weigh magnesium oxide, chromium trioxide, aluminum oxide, gallium oxide, lithium carbonate and silicon dioxide according to stoichiometric ratio, add 5-8% flux of the total mass of raw materials, place in a high-energy ball mill, and ball mill for 2-3 hours under nitrogen atmosphere at a speed of 300-400 r / min to obtain mixed powder;
[0013] (2) The mixed powder is loaded into a boron nitride crucible and placed in a tube furnace. It is pre-fired at 500°C for 2 hours in an air atmosphere, and then nitrogen gas with a purity of ≥99.99% is introduced. The temperature is raised to 1450-1550°C and held for 6-8 hours at a rate of 5°C / min.
[0014] (3) After cooling to room temperature, the sintered product was soaked in 1 mol / L dilute nitric acid for 30 min, filtered and washed until neutral, and dried at 120℃ for 4 h to obtain the target phosphor.
[0015] The flux mentioned in step (1) is a mixture of ammonium fluoride and lithium fluoride in a mass ratio of 3:1.
[0016] The present invention also provides a near-infrared light-emitting diode, including a blue light chip and a rare earth-free ultra-wideband near-infrared phosphor, wherein the rare earth-free ultra-wideband near-infrared phosphor is mixed with silicone at a mass ratio of 1:4 and coated on the chip surface, and the device has a photoelectric conversion efficiency of ≥17% and an output power of ≥190mW.
[0017] The specific technical effects of this invention are as follows:
[0018] (1) Rare earth-free design: avoids dependence on rare earth resources, reduces raw material costs by more than 40%, and conforms to the trend of green development;
[0019] (2) Performance breakthrough: emission half-width ≥200nm, internal quantum efficiency ≥96%, thermal stability at 180℃ remains above 88%, which is superior to existing similar products;
[0020] (3) Simple process: The preparation process does not require complex equipment, and the step-by-step sintering process improves the repeatability of the product, making it suitable for industrial production. Detailed Implementation
[0021] The specific technical solutions of the present invention will be described with reference to the embodiments.
[0022] Example 1
[0023] Weigh out 0.97 mol of magnesium oxide, 0.015 mol of chromium trioxide, 1.4 mol of aluminum oxide, 0.6 mol of gallium oxide, 0.03 mol of lithium carbonate, and 0.05 mol of silicon dioxide according to the stoichiometric ratio. Add 6% of the total mass of the raw materials as flux (ammonium fluoride:lithium fluoride = 3:1). High-energy ball milling is performed for 2.5 h (350 r / min) under nitrogen atmosphere. The mixed powder is placed in a boron nitride crucible and pre-fired at 500℃ in air atmosphere for 2 h. Then, nitrogen gas is introduced to raise the temperature to 1500℃ and hold for 7 h. After cooling, soak in 1 mol / L dilute nitric acid for 30 min, wash and dry to obtain phosphor.
[0024] Performance testing: Under 460nm blue light excitation, the emission spectrum is 700-1100nm, the full width at half maximum is 215nm, the internal quantum efficiency is 97.2%, and the luminescence intensity at 180℃ remains at 89.5% of the room temperature.
[0025] Example 2
[0026] The amount of gallium oxide was adjusted to 0.4 mol, the amount of silicon dioxide was adjusted to 0.04 mol, the sintering temperature was 1480℃, and the other conditions were the same as in Example 1.
[0027] Performance testing: emission half-width 208nm, internal quantum efficiency 96.5%, thermal stability 88.3% at 180℃.
Claims
1. A rare-earth-free ultrawideband near-infrared phosphor, characterized in that, The general chemical formula is: , where 0.005≤a≤0.03, 0.2≤b≤0.8, 0.01≤c≤0.05, and 0.02≤d≤0.
08.
2. The rare-earth-free ultrawideband near-infrared phosphor according to claim 1, characterized in that, The phosphor has a spinel-type crystal structure with a lattice constant a = 8.08-8.12 Å, and trivalent chromium ions exist as weak field centers.
3. The method for preparing a rare-earth-free ultrawideband near-infrared phosphor according to claim 1 or 2, characterized in that, Includes the following steps: (1) Weigh magnesium oxide, chromium trioxide, aluminum oxide, gallium oxide, lithium carbonate and silicon dioxide according to stoichiometric ratio, add 5-8% flux of the total mass of raw materials, place in a high-energy ball mill, and ball mill for 2-3 hours under nitrogen atmosphere at a speed of 300-400 r / min to obtain mixed powder; (2) The mixed powder is loaded into a boron nitride crucible and placed in a tube furnace. It is pre-fired at 500°C for 2 hours in an air atmosphere, and then nitrogen gas with a purity of ≥99.99% is introduced. The temperature is raised to 1450-1550°C and held for 6-8 hours at a rate of 5°C / min. (3) After cooling to room temperature, the sintered product was soaked in 1 mol / L dilute nitric acid for 30 min, filtered and washed until neutral, and dried at 120℃ for 4 h to obtain the target phosphor.
4. The method for preparing a rare-earth-free ultrawideband near-infrared phosphor according to claim 3, characterized in that, The flux mentioned in step (1) is a mixture of ammonium fluoride and lithium fluoride in a mass ratio of 3:
1.
5. A near-infrared light-emitting diode, characterized in that, The invention includes a blue light chip and a rare earth-free ultra-wideband near-infrared phosphor as described in claim 1, wherein the rare earth-free ultra-wideband near-infrared phosphor is mixed with silicone at a mass ratio of 1:4 and coated on the chip surface.